1. Field of the Invention
The present invention relates to a flip chip type semiconductor device and a method of manufacturing the same. In particular, the present invention relates to a flip chip type semiconductor device, from which a semiconductor chip can be recovered, having excellent mounting reliability, and a method of manufacturing the same.
2. Description of the Related Art
In a flip chip type semiconductor device, protruding bumps are formed with a metallic material such as a solder, Au, Snxe2x80x94Ag alloys or the like on external terminals formed in the periphery of the semiconductor chip or external terminals formed in a prescribed area array on an active region. Such a flip chip type semiconductor device is mounted by an end user on a multi-layer wiring board on which electrode pads are arranged in the same pattern as the bumps on the flip chip type semiconductor device. When a solder is used as a bump material to mount the flip chip type semiconductor device on the multi-layer wiring board, in general, bonding is carried out by an IR (infrared ray) reflow process, in which a flux is used and the bumps are heated to a prescribed temperature.
However, when the flip chip type semiconductor device is mounted on the multi-layer wiring board, stress distortion occurs due to a difference in linear expansion coefficients of the multi-layer wiring board and the flip chip type semiconductor device. Consequently, cracks occur at the interface between the flip chip type semiconductor device and the bumps. Therefore, mounting reliability, particularly, a temperature cycle characteristic of the flip chip type semiconductor device is degraded. Furthermore, since thermal and mechanical stresses upon mounting are applied to the semiconductor chip as well, the semiconductor chip, particularly, a passivation film and an active region surface under the passivation film are damaged.
In order to solve these problems, a technique has been conventionally proposed that a ceramic material such as AlN (aluminum nitride), mullite, glass ceramic or the like is used as a material for the multi-layer wiring board to minimize the difference in linear expansion coefficients between the material of the multi-layer wiring board and silicon, thereby minimizing the stress distortion. Thus, mounting reliability is improved.
Even though the mounting reliability is improved, however, cost is a problem in this technique since an expensive ceramic material is used as a material for the multi-layer wiring board. Therefore, in general, application of this technique is limited to fabrication of a high-priced super computer or large-scale computer.
On the other hand, recently, a technique is widely being utilized that an organic material, which has a high linear expansion coefficient but is relatively inexpensive, is used as a material for the multi-layer wiring board, and then an underfill resin is disposed between this multi-layer wiring board and a semiconductor chip. In this technique, the disposition of the underfill resin between the semiconductor chip and the multi-layer wiring board composed of organic material makes it possible to distribute a shearing stress imposed on bump bonding portions disposed between the semiconductor chip and the multi-layer wiring board. Thereby, mounting reliability is improved. This technique enables use of a multi-layer wiring board composed of inexpensive organic materials.
However, the above-described technique using an underfill resin has problems described below.
Firstly, it is difficult to recover a semiconductor chip. Since a high-performance LSI (large scale integrated circuit) is generally used as a flip chip type semiconductor chip, the semiconductor chip itself is expensive. Therefore, if a semiconductor chip is mounted on the multi-layer wiring board and then a defective site is detected in a portion other than the semiconductor chip during an electric screening process, the non-defective semiconductor chip needs to be recovered and reused. For example, if defective bonding is detected in a solder bump portion, the semiconductor chip needs to be peeled off and then bonded again. However, recovery of a semiconductor chip is technically difficult in the above-described structure of the flip chip type semiconductor device, in which an underfill resin is interposed between the semiconductor chip and the mounting board.
FIGS. 1A and 1B are sectional views showing a method of mounting a conventional semiconductor device on a multi-layer wiring board. FIG. 1A shows the semiconductor chip. As shown in FIG. 1A, outer solder electrodes 13 are formed on the bottom surface of a semiconductor chip 24. FIG. 1B shows a state that the semiconductor chip 24 is mounted. As shown in FIG. 1B, the semiconductor chip 24 is mounted and bonded onto a mounting board 25 by melting the solder bumps while the outer solder electrodes 13 are positioned on electrode portions (not shown) on the mounting board 25. An underfill resin 26 is filled between the semiconductor chip 24 and the mounting board 25. That is, the outer solder electrodes 13 are buried in the underfill resin 26.
FIG. 1C is a sectional view showing a method of recovering the semiconductor chip 24. To recover the semiconductor chip 24, as shown in FIG. 1C, the rear surface of the semiconductor chip 24 is suctioned by a heating/suctioning tool 27 for repair while heated. Then, the semiconductor chip 24 is pulled up while the bump bonding portions are being melted. Thus, the non-defective semiconductor chip 24 is removed from the mounting board 25.
FIG. 2 is a sectional view showing a state after the semiconductor chip 24 in the conventional flip chip type semiconductor device is removed from the mounting board 25. As shown in FIG. 2, when a chip is removed from a semiconductor device having an underfill resin, problems arise that the outer solder electrodes 13 remain buried in the underfill resin 26, the underfill resin 26 and the mounting board 25 are damaged and so forth. Therefore, the non-defective semiconductor chip 24 cannot be reused. With the above-described reasons, it is difficult to reuse a non-defective flip chip type semiconductor chip in the conventional technique.
Secondly, if voids exist in the underfill resin 26 or a bonding characteristic is unfavorable at the interface between the underfill resin 26 and the semiconductor chip 24 and the interface between the underfill resin 26 and the mounting board 25, a peeling phenomenon is induced at the aforementioned interfaces in a hygroscopic reflow process for a product. Thus, a non-defective product becomes defective.
Thirdly, since a process of heating to a high temperature is performed when the semiconductor chip 24 is recovered, barrier metal-bonding portions of the removed semiconductor chip 24 and the outer solder electrodes 13 as well as a passivation film (not shown) are damaged. Thus, a non-defective semiconductor chip may become defective. The passivation film is formed for the purpose of protecting the active region of the semiconductor chip 24 and composed of PI (polyimide) organic material or inorganic material such as an SiO material such as SiO, SiO2 or the like. Furthermore, thermal and mechanical loads applied to the outer solder electrodes 13 are transmitted to the semiconductor chip 24, and thus a non-defective semiconductor chip 24 may become defective. In this case, peripheral devices including the mounting board 25 may also become defective.
Therefore, in reality, use of an organic material as a material for the multi-layer wiring board cannot lead to a lower cost.
When a ceramic multi-layer wiring board is used, recovery of a non-defective semiconductor chip is relatively easy since use of an underfill resin is not required due to optimization of the linear expansion coefficient of the ceramic material.
An object of the present invention is to provide a low-cost flip chip type semiconductor device in which an underfill resin is not used, mounting reliability is excellent since cracks due to a thermal stress can be prevented at the interface between a semiconductor chip and solder bumps and the semiconductor chip can be recovered, and a method of manufacturing the same.
The flip chip type semiconductor device according to the present invention comprises a semiconductor chip provided with pad electrodes, an insulating resin layer covering a semiconductor chip surface on a side on which the pad electrodes are provided, metallic posts which penetrates through this insulating resin layer and are connected to the pad electrodes and electrodes which are provided on the insulating resin layer surface and connected to the metallic posts. The metallic post has a first portion buried in the insulating resin layer and a second portion projected from the insulating resin layer. It is noted that when xe2x80x9cmetalxe2x80x9d is referred to in the present invention, not only pure metals but also alloys are included.
In the present invention, a mounted semiconductor chip can be recovered since an underfill resin is not provided. Furthermore, since an underfill resin is not provided, there is no problem of a peeling phenomenon due to voids in the underfill resin or defective bonding between the underfill resin and a semiconductor chip or a mounting board. Furthermore, an insulating resin layer and metallic posts are disposed between the pad electrodes of the semiconductor chip and externally exposed electrodes. Ends of the metallic posts are projected from the insulating resin layer surface. Therefore, a layer composed of the metallic posts and the insulating resin layer serves as a stress relaxation layer so that thermal and mechanical loads imposed on the externally exposed electrodes can be prevented from transmitting to a semiconductor chip. Furthermore, since a contact area between the metallic post and outer solder electrode making contact with the metallic post is large and, moreover, damage to the outer solder electrode due to a horizontal stress and thereby propagation of cracks can be prevented, bond strength between the metallic post and outer solder electrode can be increased. Therefore, mounting reliability of the flip chip type semiconductor device can be improved. Consequently, a flip chip type semiconductor device from which a semiconductor chip can be recovered and which has excellent mounting reliability can be provided without using an expensive ceramic substrate.
In this flip chip type semiconductor device, centroids of the aforementioned first and second portions may be deviated from each other in a plane view. Consequently, the metallic post can be divided into two portions. Therefore, thermal and mechanical loads transmitted to the semiconductor chip via the metallic post can be further reduced and the aforementioned effect can be further enhanced.
In a method of manufacturing a flip chip type semiconductor device according to the present invention, a plurality of recessed portions are formed in the surface of a metallic substrate, and a metallic post is formed on the surface of each recessed portion. Then, this metallic post and a pad electrode of a semiconductor chip are connected, an insulating resin layer is formed by filling an insulating resin into a space between the metallic substrate and the semiconductor chip, the metallic substrate is removed and electrodes are formed on the metallic post.
In another method of manufacturing a flip chip type semiconductor device according to the present invention, a plurality of projected portions on a first surface of a metallic substrate, a plurality of projected portions corresponding to the projected portions formed on the first surface are formed on a second surface of the metallic substrate, and the projected portions formed on the first surface and pad electrodes of a semiconductor chip are connected with each other. Then, an insulating resin layer is formed by filling an insulating resin into a space between the metallic substrate and the semiconductor chip, the projected portions are partitioned by removing portions of the metallic substrate other than the projected portions and electrodes are formed on the projected portions formed on the second surface of the metallic substrate.
Consequently, the aforementioned flip chip type semiconductor device can be efficiently fabricated.
The plurality of projected portions may be formed by forming a resist for masking regions where the projected portions are to be formed and etching the metallic substrate by using this resist as a mask.